Strong quakes shake New Zealand

Two strong earthquakes, one measuring 6.6 and then a 5.7, hit central New Zealand on Friday afternoon, sending Wellington commuters fleeing from the city and causing havoc in Marlborough.

Police said some buildings were severely damaged in Seddon, which has been the centre of seismic shaking since a magnitude 6.5 tremor struck on July 21.

Power was out in many parts of Marlborough and State Highway 1 was closed between Weld Pass, just south of Blenheim, and Seddon due to dangerous overhangs, slips, large boulders and cracks in the road.

The police station, library and main sports stadium in Blenheim have been evacuated.

Windows in a Wellington building have broken as a result of the earthquake. Photo: Amy Jackman / Fairfax NZ

Geonet said the big quake stuck at 2.31pm local time and nearly two hours later it was graded as a 6.6, after initial readings of 6.9 and then 6.2. Its centre was 10 kilometres south-east of Seddon at a depth of eight kilometres.

While aftershocks continued apace after the 6.2, a 5.7 rattler at 3.52pm local time in Wellington caused further alarm.

Further north, a series of earthquakes, including some centred in the Rangitikei region, cut power to Hunterville.

Within half an hour of the major earthquake, a shallow 4.2 magnitude earthquake also shook Hunterville, followed by ones near Turangi and Ohakune.

Then at 3.09pm local time, a ‘‘severe’’ earthquake hit north of Taihape. It was a 4.9 magnitude earthquake at a depth of 13 kilometres, Geonet said.

A further aftershock was reported by Geonet near Levin at 3.27pm local time.

The 4.5 magnitude shake was centered 10 kilometres north-east of the Horowhenua at a depth of 29 kilometres.

There was no tsunami threat and Civil Defence said its headquarters had not been activated.

'It was horrific'

Gillian Bruning was sitting outside the Cosy Corner Cafe in Seddon when the quake hit and the windows were smashed out. ‘‘It was horrific, we had two Australian tourists in there when it hit and I had to run in and get them out.’’

A Civil Defence team and Marlborough District Council building team have headed to Seddon.

Two empty houses, one in Seddon and nearby Ward, have been seriously damaged. An engineer is checking the Haldon Dam.

Children were in the Seddon School hall when the first earthquake hit and everyone started screaming.

Paige Jackson, 9, said she was lying on top of other children and a light fell on them.

A welfare centre has been set up at Seddon School.

Blenheim police have cordoned off the Forum on Market Street, and sent all shop owners and staff home because of two large cracks that appeared on the flyover between Paper Plus and the National Party electorate office.

Blenheim police sergeant Graham Single said they were moving through central Blenheim, checking for further evidence of damaged buildings, and ensure people were safe.

‘‘We're going to make our way through the town and ensure people are safe and sound and for anyone that needs help,’’ he said.

People are leaving town, walking down the middle of the street to avoid buildings and power lines. Power is out in many areas and phones are struggling to cope.

People are advised to communicate by text message rather than phone calls.

Wellington workers flee buildings

The 6.6 quake saw workers fleeing their buildings and queues of traffic were forming out of the capital.

Wellington buildings sustained minor damage including broken windows.

Some people were trapped in lift shafts, Fire Service Region manager Brendan Nally said.

On Wellington’s waterfront, cranes swayed and the city seemed to groan.

Joggers stopped in their tracks and struggled to stand. Amanda Beeslaar, a visitor from Auckland, said the quake was ‘‘terrifying’’.

‘‘It felt like a jet plane coming over and them it just started shaking. I thought the earth was going to open up,’’ she said.

Sam Stanley was in the NZX building when the quake hit.

‘‘I feel a bit queasy, it was swaying so much. I waited about 10 seconds and got under my table, then we decided to get out,’’ he said.

Traffic backed up

New Zealand Transport Agency central region spokesman Anthony Frith said state highway networks were being checked and reports so far were that they remained in good condition.

Wellington motorists were being advised to be patient and to expect delays.

Reports were coming in of heavy traffic northbound from Wellington, Frith said.

‘‘We have heard that it is starting to get quite congested. It’s probably yet to reach its peak so if people can delay their travel they should but obviously if you need to get home to check on loved ones that's absolutely understandable.’’

Updates were being posted on NZTA’s website and on social media.

Trading on all markets on the New Zealand stock exchange was halted briefly before resuming.

A spokeswoman for St John’s southern communications centre said staff were ‘‘not particularly busy’’, but had been checking stations around the South Island.

‘‘Everyone’s OK,’’ she said.

'Felt it' reports

There were hundreds of ’’felt it’’ reports on the Geonet website, including reports as far south as Dunedin and as far north as Auckland.

Geonet seismologist Anna Kaiser said ‘‘very preliminary’’ data showed Friday’s earthquake was a little further west than the 6.5 earthquake on July 21, but it was certainly another event in the Cook Strait sequence.

Typically with a 6.5 earthquake the aftershocks would be expected to be up to 1 magnitude lower. ‘‘This is a slightly larger event,’’ she said.

A final magnitude reading for Friday’s quake was needed before deciding whether it could be classed as an aftershock of the 6.5 quake. It was certainly related to the 6.5 quake.

‘‘The 6.5 can alter the state of the stress in the surrounding area,’’ Kaiser said.

‘‘Because the stress has been altered you can get another event like this, although typically you would see just a normal aftershock sequence. This looks like it was slightly larger than what you would expect to get,’’ she said.‘‘Certainly following an event like this you do expect a sequence of aftershocks.’’

That could be expected to continue for the next day or two, with magnitude 5 earthquakes possible.